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HARBOUR PORPOISE RESEARCH - 1997
CONTENTS:
MAIN OBJECTIVES IN 1997
HARBOUR PORPOISE RELEASE PROGRAM
CRITICAL HABITAT
FORAGING BEHAVIOUR
AN AGING FLEET

MAIN OBJECTIVES IN 1997:

  • Assist local fishers with the safe release of harbour porpoises from herring weirs
  • Identify critical habitat areas used by porpoises in the Bay of Fundy, with the hope of applying this information to a management strategy for this population
  • Obtain detailed information on the foraging behaviour of harbour porpoises in the Bay of Fundy during focal animal follows of wild harbour porpoises equipped with advanced time-depth recorders (TDRs)
HARBOUR PORPOISE RELEASE PROGRAM:

Field research ran from July 8 to September 26. Each day the weather permitted, we monitored all of the weirs on the northern and eastern sides of Grand Manan for the presence of porpoises. The number of entrapped harbour porpoises was higher than in 1996 approaching more normal entrapment figures for other years (Table 1). We do not know why the entrapment rate fluctuates from year to year but we assume that it is related to herring densities in near-shore waters. This has increased our awareness of the dynamic nature and complex interactions between porpoises, their environment and their prey, and highlighted the need to consider these issues concurrently.

We successfully released 20 of 22 porpoises, two died during seining process. We also had three minke whales in weirs, all successfully released. Each of the whale releases was accomplished using our specially designed marine mammal seine and we attributed our success to the use of this net. In the past minke whales often became entangled in herring seines and died in weirs but we have now developed a protocol that can be used to ensure their safe release in coming years.

CRITICAL HABITAT:

Five porpoises were fitted with satellite tags. The transmitters lasted for 42, 92, 122, 144, and 171days. The track data for three of the porpoises, including maps can be found on WhaleNet .

The satellite tracks represent important steps forward in understanding how harbour porpoises utilize habitat in summer and fall. As well as confirming some previous conclusions, we have identified some new important features of harbour porpoise movements from these tracks.

  • Porpoises from previous satellite deployments never returned to the Bay of Fundy after leaving, however, during 1997 three individuals returned after making brief trips into the Gulf of Maine. This was not surprising because previous tracks had shown that these animals were extremely mobile. This information reinforces the need for coordinated harbour porpoise management between the United States and Canada.
  • Harbour porpoises tagged in 1997 utilized wider portions of the Gulf of Maine than had been previously documented. This underscores the importance of this entire region to this stock of harbour porpoises. Unfortunately this is also a region where fishing activities, especially gillnet fishing, are intense. Many tagged porpoises moved directly from Canadian to US fishing area seriously increasing each porpoise's individual risk of entanglement. The results we present here confirm our previous conclusions that porpoises are at risk of entanglement for a significant portion of the year.
  • We were able to collect the first significant track from a female harbour porpoise this year (92 days). Although we have yet to do a thorough analysis, it is clear from her track that she utilized as wide a geographical region as the tagged male porpoises. This is particularly interesting because we had suspected that there might be gender-based differences in habitat utilization patterns in this species. From this initial track it would appear that this is not the case. One important caveat is this female was immature. Mature females that are pregnant and/or lactating might show different patterns. We hope to tag some mature females during 1998 to address this issue.
Special thanks to the weir fishers who support the HARBOUR PORPOISE RELEASE PROGRAM.

Our sympathy is extended to the family of the late David Bass, a local weir fisher who supported our program from its outset.

FORAGING BEHAVIOUR:

Unfortunately, we did not experience similar success with the foraging study. Although we deployed three self-releasing time-depth recorders on harbour porpoises we were unable to recover any of these units. This was in sharp contrast to our previous TDR study in which we recovered all nine units we deployed. After these initial failures we chose to suspend further deployments until these problems could be resolved. It was discovered that a design flaw in the floatation component of the package prevented them from floating when the packs came loose. We believe the floatation material compressed when the porpoises dived to depth making the packs negatively buoyant.

During the TDR deployments we were able to follow the tagged porpoises with relative ease and the protocol we developed worked very well during each of the follows. The packs had a special magnesium linkage which slowly dissolved in the seawater allowing the packs to release from the porpoises after 10-12 hours. In each deployment the packs detached from the porpoise close to the predicted release time. We are confident that with the modification that are currently underway to the design, we will be successful in our deployments during 1998.

AN AGING FLEET:

Although we replaced one of our old boats a couple of years ago, we are now in desperate need of replacing an aging speed boat. We use the speed boat to check herring weirs daily for the HARBOUR PORPOISE RELEASE PROGRAM, and as a second seine boat when we are needed at more than one herring weir or when there are numerous porpoises in one weir. We have applied for funding for both boat and engine and so far have had been awarded funding from the George Cedric Metcalf Charitable Foundation and the T.R. Meighen Foundation. We are awaiting one additional source before any purchases can be made.

About the Grand Manan Whale and Seabird Research Station Research Station

The Grand Manan Whale & Seabird Research Station (GMWSRS) is a non-profit research facility located in North Head. The GMWSRS was founded in 1981 by the late Dr. David Gaskin, a professor at the University of Guelph, Ontario and a pioneer of harbour porpoise research on Canada's east coast. Since 1981, the research station has conducted research on harbour porpoises, right whales, seals and seabirds in the Grand Manan Archipelago.


HAVE A GOOD WINTER AND WE'LL SEE YOU NEXT SUMMER!


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Harbour Porpoise Research:
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GMWSRS
Grand Manan Whale & Seabird Research Station Inc.
24 Route 776, Grand Manan, NB, Canada, E5G 1A1
www.gmwsrs.org
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© 2004 Grand Manan Whale & Seabird Research Station Inc.

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